4 Answers
4

Forced Movement: If the mount is pulled, pushed, or slid, the rider moves with it. If the rider is pulled, pushed, or slid and the mount isn’t, the rider can have the two of them move together. Otherwise, the rider is dismounted and falls prone in the destination space of the forced movement.

The mount and rider are considered separate creatures and are targeted independently. (RC p254)

The attack sequence if multiple targets are involved is on pg214 of the Rules Compendium. Simplified it is:

chose targets

roll and resolve an attack on one target

repeat step 2 on a different target until finished.

In the case of a mount and rider you should fully resolve the attack against one before going onto the other. If the mount is slid left and the rider slid right, they will likely end up right back where they started.

In the case of teleportation, (which is not forced movement). It is covered on pg255 of the Rules Compendium. In short they teleport separately, teleport the mount and the rider is dismounted and falls prone.

By your analysis of the "multiple target" process, one could say that a one of the creatures involved was moved out of the area of effect (via its attachment to the other) prior the attack against it, even though both are being attacked by a single burst/blast. How do you resolve that? Either the events occur simultaneously or they don't - which is it? And, what would then happen if the mount was slid backward while the rider was slid sideways?
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IsziOct 21 '10 at 7:15

1

I did condense a 6 step process down to 3 to show how I thought this should be resolved. It seems clear that the initial choosing of targets is sufficient to resolve questions about range and LoE. After that, you just resolve against each creature regardless of where they are currently standing. For me, this is a new section of rules that I hadn't known about. I'd always been curious as to the "correct" way to resolve a Thunderwave against many critters for example. Mounts and riders may be a unique case that exposes some fugly situations. I'd have no objection to a DM houseruling here.
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Pat LudwigOct 21 '10 at 13:44

Yeah, I expect the response from WotC will leave a lot of this to DM houserule. Even when one particular ruling seems the most sensible, they're not shy about reminding you that the DM is the final arbiter.
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IsziOct 21 '10 at 14:13

Based on current RAW, the answers aren't quite as simple as the questions - in fact, part of them brings up another question which I'll be shortly sending to WotC support.

First, let's break up your first question a bit:

1a. Are a rider and mount considered different targets?

Yes. For the purposes of targeting, the rider and mount are separate entities. If you have a power that targets one creature, you must choose either the mount or the rider. If you have a power that targets all creatures within a burst or blast that includes the mount & rider's space (remember, they share the same space) then you must roll separate attacks for each.

1b. Can you force a dismount by forcing movement of one but not the other?

It depends.

For a push, pull, or slide:

If the target is the mount, then the rider generally moves with it.

If the target is the rider, then the rider has the choice of whether to bring the mount along, or to go on his own. If the rider chooses to move separately, he is dismounted and falls prone in the destination space.

For a teleport (technically not "forced movement", but can be involuntary):

When only one of the two is targeted, the other does not teleport with it.

If the mount teleports without the rider, the rider is dismounted and falls prone.

2 If I can push the rider off of the mount, would the "Catching yourself"(PHB p284) clause kick in and give the rider a save from the fall?

I'm certain the answer to this would be "no". This being because, in most cases, (push, pull, slide) a rider's separation from the mount due to forced movement is the rider's choice - it either happens or it doesn't, no save involved.

In the case of a teleport, there is only one situation in which the rider would explicitly be dismounted and fall prone. This is when the mount is the target of the teleport. Since the mount is the creature being affected, and rules specifically state that rider and mount are not teleported together, the rider has no choice in the matter - he dismounts and falls prone.

In any case, the "Catching Yourself" clause would not even be effective for forced dismounts, since a successful save still leaves the target prone in the last space occupied prior to the fall.

Some scenarios not explicitly covered in RAW:

What if the rider is teleported without the mount? (Presumably, the rider would land standing in the destination square, if no other rules or effects apply.)

(Wizards Customer Support): "1. Since it is not specified, it will be up to your DM to decide. However, Since they are the one being teleported, and are not prone to begin with, they would remain upright."

What if the rider and mount are teleported to the same destination, by a burst or blast? (Teleportation is instantaneous, so I would venture to guess the rider could stay mounted.)

(WCS): "2. Again, it's the DM's call. If it is a player's or allies power that causes the teleport, I would go with that they remain together."

What if the rider and mount are subjected to conflicting movement? (i.e.: Rider is slid left, while mount slides right.)

(WCS): "3. As written, if they are both affected and moved in different directions, the rider will fall prone."

After reading the rules on this one more closely, I see it is a direct RAW interpretation. The key lies in this bit:

(Essentials Rules Compendium, p. 254, emphasis mine)
“Even though the mount and rider occupy the same space, they are still separate creatures and are targeted separately. … If the mount is pulled, pushed, or slid, the rider moves with it. If the rider is pulled, pushed, or slid and the mount isn’t, the rider can have the two of them move together. Otherwise, the rider is dismounted and falls prone in the destination space of the forced movement.”

In this case, the condition being triggered is that the rider is being moved, and the mount is also. This overrides the "mount carries rider" clause, and violates the "rider chooses whether they move together" clause. Therefore the two are separated, the rider is dismounted, and falls prone.

What if one of them is restrained, when the other is pushed, pulled or slid? (This is the only combat condition that renders a creature immune to forced movement. However, teleportation can still take place.)

(WCS): "4. The restrained creature would remain while the other is moved."

All of the data to support my conclusions thus far, are taken from WotC Customer Support e-mails, and the following Rules Compendium sections:

Reminder - teleportation is not forced movement. As you've demonstrated it poses a different set of problems and should be addressed in a different question IMHO.
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Pat LudwigOct 21 '10 at 6:26

Though "teleportation" is not technically a part of "forced movement" by glossary definition, I consider any type of "involuntary movement" to be "forced movement" for purposes of discussion. This way, all bases are covered for readers who may be unfamiliar with that particular technicality.
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IsziOct 21 '10 at 6:35

2

The teleportation rules on pg255 cover the scenarios you raise above. You should not conflate teleportation with forced movement. The rules are similar in some cases, but not others.
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Pat LudwigOct 21 '10 at 6:39

If only one of the two (mount and rider) is subjected to forced movement then generally no you cannot force a dismount (as explainied by Pat). But imho that doesn't fully address the more general question (Can forced movement be used to dismount a rider).

If you are using an attack that can target more than one creature, it gets more complicated (mount and rider are targeted separately and therefore bursts and blasts can affefct both of them). Certainly it can be argued that the rule states that if the mount is subject to forced movement then the rider can always simply ignore any competing forced movement - although it's not clear that is the intent. Likewise, what happens when the mount is immobilized and the rider is subject to forced movement - the rider can't have the two of them move together - is he then dismounted?

What makes sense to me (and I leave it to each DM to decide to what degree in-game logic versus strict and literal interpretation of the RAW impacts their rule decisions) is the following: If the mount is immobilized, forced movement can force the rider off of the mount. If the rider is immobilized, it can ride along with the mount as it is moved. If both are subject to forced movement and moved in opposing directions the rider can be dismounted.

It may not be strict RAW, but the rules are not and cannot be 100% comprehensive and I feel this specific sub-question is not explicitly covered by the RAW.

Forced movement is immune to Immobilized. Perhaps you might want to modify your example to Restrained? (It's not spelled out in the "Forced Movement" entry in D&DI Compendium, but if you look under the "Immobilized" and "Restrained" entries you see that Restrained is the only condition that does not allow forced movement.)
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IsziOct 21 '10 at 6:33

If the rider is pulled, pushed, or
slid and the mount isn’t, the rider
can have the two of them move
together. Otherwise, the rider is
dismounted and falls prone in the
destination space of the forced
movement.

I believe that you can dismount a rider, when and because the rider "cannot" move her mount all the way. After a while people see my point of view.

Hey Mark! The situation where mount can't move with the rider because of size or space is an interesting edge case and I agree it's covered by Otherwise, the rider is dismounted and falls prone... Thanks!
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yhw42Nov 11 '10 at 6:00